Virtually all vehicles today (cars, trucks, trains, airplanes, boats etc) incorporate one or more windshield wipers which can be deactivated at any time by a driver to sweep repeatedly across an exterior surface of the windshield. A rubber or plastic wiper blade of each wiper assembly engages the exterior surface to clear debris from that portion of the windshield generally in front of the driver to maintain unimpaired visibility. Debris left to build up on the windshield impairs visibility for the driver and if permitted to build up anywhere on the wiper assembly can also reduce wiping efficiency. Maintaining good visibility for the driver lessens the chances of the vehicle becoming involved in an accident and hence increases the safety level for all occupants.
The type of debris which can accumulate depends on the geographical location and season. In particular, in parts of the world where winter weather is severe, snow and ice build up on wiper blades is a common experience. In particularly extreme weather conditions, it is not uncommon for snow or ice to freeze to a windshield wiper arm and/or wiper blade. While allowing for movement of the blade across the windshield, such frozen debris may seriously reduce the cleaning action of the blade on the windshield surface. Such freezing may occur while a vehicle is being driven or when stationary. Also, it is common for lumps of ice or snow to become lodged under a wiper blade during use so as to be carried with the blade on its wiping movement. This situation may occur if the blade in moving across the windshield surface is caused to ride onto a mass of ice or snow and move it from a stationary location upon the windshield.
As long as an ice or snow mass remains lodged the efficiency of the wiper blade is severely reduced as a significant portion or all of the wiper blade can no longer engage the exterior surface of the windshield. The thickness of any mass of ice or snow may have a bearing on the wiping efficiency especially if the mass extends along a significant length of the blade. Ice lumps as small as one millimeter if lodged can cause the wiper to experience reduced efficiency. Snow and/or ice formation anywhere on the windshield wiper assembly may contribute to reducing wiping efficiency also by raising sections of the blade off the windshield.
A driver of a vehicle when experiencing any of the problems discussed above generally has two options. The first and safest option is to stop the vehicle and, even in extremely cold conditions, exit the vehicle to manually break away the ice or snow frozen to or trapped beneath the wiper blade. This is not always convenient and is certainly not possible for pilots and train operators. Even when driving a road vehicle there are times when stopping to remove debris from a windshield is impossible due to inherent danger. For instance, bridges or certain roadways have little or no shoulder area and when busy with traffic, a driver may not stop safely. Even when there is room to stop by the roadside, it may not be prudent to do so as personal safety may be at risk if the driver leaves the vehicle or if his parked position may present a driving hazard to other vehicles.
A common although unrecommended solution for many drivers is to open a window and manually attempt to grasp a windshield wiper as it travels within extended reach of the driver. In reaching the wiper, the driver attempts to lift it momentarily from the windshield in the hope that the debris will become dislodged. Needless to say this is an extremely unsafe practice and, in many cases, such as for larger vehicles, e.g. trains and airplanes, is simply not an option.
A further problem concerns the coating of a windshield wiper assembly with ice or snow when the wiper asembly is in the parked position during storm conditions. The thickness of the ice or snow may be such as to trap the wiper assembly in the parked position and thus prevent its operation when the operating motor is energized. It can be an extremely tedious and unpleasant operation for a driver to need to free the wiper manually from the parked position in winter conditions. To ease this problem, some car manufacturers incorporate heating elements in windshield glass. The elements function to heat windshields in a manner similar to that of present day electrical rear window defrosters. This solution is not only expensive and extremely slow in effective operation, it cannot dislodge or melt ice or snow while the wiper assembly is in operation. Furthermore, windshield heating elements are ineffective in releasing wipers from ice or snow when in their parked positions if the wiper blades are not in engagement with the windshields.
Other solutions, such as in U.S. Pat. No. 5,325,561 issued to Kotlar, teach electrically heating various portions of a wiper blade to melt away snow and ice. Although this solution is somewhat effective when the wipers are in operation, it is an extremely slow operation. This solution can also be very expensive for the owner of the vehicle as wiper blades wear away and should be replaced regularly. Wiper blades of the type taught in the above patent would incorporate an integral electrical heating element thereby drastically increasing the cost of replacement blades.
In addition, headlights on some cars incorporate a small wiper arrangement to clean the exterior glass surfaces of the headlights. Headlight wipers may suffer severe ice buildup in winter climates and very often cannot be operated as they become frozen in position. Their proximity to the ground and front end location places them directly in the path of snow, slush and ice raised by passing vehicles or vehicles in front.